Since the completion of the Human Genome Project in 2003, scientists have been crunching numbers and exploring the genetics of anything and everything that makes us human.
The data are being used for everything from developing medications and treatment to looking for the specific genes that cause or make us prone to diseases such as diabetes or bipolar disorder.
Finding answers is not an overnight thing. Humans have 20,000-25,000 genes to sift through and some of those could be junk genes that don’t actually code for DNA. Some diseases are easier to decode than others. For example, Huntington’s disease is related to only one gene, which can be identified with a simple blood test. When it comes to bipolar disorder, however, the hunt gets a little more cloudy.
There are seven genes thought to be related to bipolar disorder that are called “candidate genes.” That does not mean that if you have those seven genes together that you will automatically have bipolar disorder. It does mean that they are suspected to be related to the cause. Part of that is because some of these same genes are also related to other mental illnesses. Bipolar disorder has been linked genetically to schizophrenia, autism, attention deficit hyperactivity disorder (ADHD) and major unipolar depression.
In case you’re curious, the specific genes in question are G72, DAOA, DISC1, NRG1, TPH2, BDNF, 5-HTT and DAT1. There are also other genes related to specific symptoms of bipolar disorder like circadian rhythm dysfunction, so that adds in other factors as well.
So, do you have the genes for bipolar disorder?
Yes. Everyone has the same genes. That doesn’t mean you’ll develop bipolar disorder.
Variation on traits such as having bipolar disorder or curly hair arise because our 20,000-25,000 genes combine in different ways. Think of it like an ice cream shop. Even if you only have two different topping options, you can combine the toppings in three different ways. If you add just one more topping option, the combinations go to seven, almost double. Five toppings brings 31 possible combinations. Now do that 20,000 or more times.
Don’t actually do that. It would take a long time with very little payoff.
Genes can also mutate. You can be born with mutations or they can develop over time. Mutations are also linked to disease. One mutation linked to bipolar disorder is found in 1 of every 200 people.
Having a genetic mutation still doesn’t mean you’ll automatically have bipolar disorder.
Bipolar disorder is thought to be caused by a combination of factors that include:
- Chemical imbalance
We’ve covered some of the genetics, and that’s a huge part. Still, even if one parent has bipolar disorder, there’s only a 4%-15% chance that a child will have it. That increases significantly if both parents have it, but it’s still not a guarantee. The other factors have to come into play.
The body’s nervous system communicates with chemicals called neurotransmitters. You’ve probably heard of a few: dopamine, norepinephrine, epinephrine (adrenaline), gaba and serotonin. There is a lot of room in the communication line for something to go wrong. That’s the chemical imbalance.
Environment is a huge concept. It’s not just about where you are sitting and what is happening around you. Environmental factors can go all the way back to the womb. If a pregnant woman gets the flu, her child is four times more likely to have bipolar disorder. It’s where you grow up, the quality of your relationships, whether you were abused as a child, if a relationship breaks up, if a loved one dies, and a sizable number of other factors.
So, you have the genes. You have the right mutations. The neurotransmitters the body uses to communicate are off. A certain something, or some things, happen in your life.
As far as we know right now, that’s how bipolar disorder is triggered. That’s how it shrinks from 100% of people having the genes thought to be associated with bipolar disorder goes down to the 2.6% of people that actually have it.
And that’s just the beginning of what it is to have bipolar disorder.
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Photo credit: NIH Image Gallery